Hydrogen-halogen exchange process



Patented May 22, 1951 ITED s'rarss er .0 FF IQE HYDROGEN-HALOGEN EXCHANGE PROCESS Delaware NoDrawing. Application May 31, 1947,

Serial No. 751,640

21 Claims. '1

This invention relates to a novel catalytic method of effecting hydrogen-halogen exchange between a polyhalogenated saturated hydrocarbon and a saturated hydrocarbon or its monohalogenated derivatives.

In one embodiment our invention relates to a hydrogen-halogen exchange process which comprises contacting a halogenated saturated hydrocarbon containing at least two halogen atoms and a member of the group consisting of saturated hydrocarbons containing more than two carbon atoms and their monohalogenated derivatives with a compound capable of yielding a free radical at a temperature at least as high as the decomposition temperature of said compound.

In a more specific embodiment my invention relates to a hydrogen-halogen exchange process which comprises contacting a halogenated saturated hydrocarbon containing at least two halogen atoms .on one of the carbon atoms and a member of the group consisting of saturated hydrocarbons containing "more than two carbon atoms and their monohalogenated derivatives with a compound capable of yielding a free radical at a temperature at least as high as the decomposition temperature of said compound.

In a still more specific embodiment my invention relates to a hydrogen-halogen exchange process which comprises contacting a halogenated saturated hydrocarbon containing .at least two halogen atoms on one of the carbon atoms and a member of the group consisting of saturated hydrocarbons containing more than two carbon atoms and their monohalogenated derivatives with. a compound capable of yielding a free radical at a temperature at least as high as the decomposition temperature of said compound and in the presence of a minor amount of an inorganic alkaline substance.

The halogenated saturated, hydrocarbons utilizable as the halogen donors in our process should contain at least two halogen atoms, and at least two of these'halogen atoms should be on one of the carbon atoms. Examples of such compounds are carbon tetrachloride, ch1oro form. hexachloroethane, 1,l.-dichlorocyclohexane, and the like. It should be noted that the polyhalogenated saturated hydrocarbons may be cyclic as well as aliphatic. In addition, the polyhalogenated saturated hydrocarbons may contain difierent halogen atoms such as are found in chlorobromoalkanes and cycloalkanes. general, the chloro compounds are preferred for reasons of economy and because yields usually are more satisfactory.

The saturated hydrocarbons or the monohalogenated derivatives thereof that are utilizable as the hydrogen donors in our process should contain more than two carbon atoms because methane and ethane and their monohalogenated derivatives are relatively unreactive. The operable compounds include propane, normal butane, isobutane, normal heptane, cyclohexane, methyl cyclohexane, bicyclo-(2,2,1)heptane, isopropyl chloride, secondary butyl bromide, chlorocyclohexane, and the like.

It can be seen that the saturated hydrocarbons may be aliphatic, monocyclic, bicyclic or polycyclic.

The catalysts that may be used in the present process comprise compounds capable of yielding free radicals at the reaction conditions. Examples of such compounds are tetraethyl lead, diazomethane, hexaphenylethane, triphenylmethylazobenzene, zinc alkyls, and cobalt alkyls. Another group of compounds ca pable of yielding free radicals are peroxy compounds, which contain the bivalent radical OO--. Examples of such compounds are the alkali metal and ammonium persulfates, perborates and percarbonates; peracetic acid, 'per-' succinic acid, dimethyl peroxide, 'diethyl peroxide, methyl ethyl peroxide, ditertiarybutyl peroxide, dipropyl peroxide, acetyl benzoyl peroxide, acetyl peroxide, propionyl peroxide, butyryl peroxide, lauroyl peroxide, benzoyl peroxide, tetralin peroxide, urea peroxide, tertiary butyl perbenzoate, tertiary butyl hydroperoxide, and methylcyclohexyl hydroperoxide. The organic peroxy compounds constitute a preferred class of catalysts for use in this invention. Only catalytic amounts, i. e., less than stoichiometric amounts, need be used in my process.

The process of this invention may be carried out in batch operation by placing a quantity of a polyhalogenated saturated hydrocarbon, a quantity of a saturated hydrocarbon containing more than two carbon atoms, or one of its monohalogenatcd derivatives, and a catalytic amount of a compound capable of yielding a free radical, in a, reactor equipped with a mixing device, heating to a reaction temperature while mixing the contents of the reactor, cooling after a suitable period of time, and recovering the products.

The preferred method of operation is of the continuous type. In this type of operation the reactants and the catalyst are continuously charged to a reactor maintained at suitable conditions of temperature and pressure. The reactor may be an unpacked vessel or coil,

or it may contain an adsorbent packing material such as fire brick, alumina, dehydrated bauxite, and the like. The products are separated from the reactor effluent and the unconverted reactants may be recycled to the reaction zone.

The temperatures employed in the process of this invention should be at least as high as the initial decomposition temperature of the compound capable of yielding a free radical. In the case of tertiary butyl perbenzoate, for example, the decomposition temperature is rather sharply defined and is approximately 115 C. On the other hand, benzoyl peroxide decomposes over a relatively wide temperature range. Usually, little advantage is gained if the reaction is conducted at a temperature more than about 150 C. higher than the decomposi ion temperature of the catalyst.

The hydrogen-halogen exchange reaction disclosed herein takes place when the reactants are in the vapor phase as well as when they are in the liquid phase. However, liquid phase operation is preferred, consequently, the pressure at which the reaction is conducted will be chosen accordingly.

The reaction times may be within the range of from slightly less than one minute to several hours. However, contact times of at least minutes usually are preferred.

There are certain modifications of our process that sometimes are useful. One such modification comprises conducting the reaction in the presence of an inorganic alkaline substance such as potassium carbonate, sodium bicarbonate, magnesium oxide, and the like. Another modification comprises carrying out the reaction in the presence of water with or without the addition of emulsifying agents.

The following examples are given to illustrate our invention but they are not introduced with the intention of unduly limiting the generally broad scope of said invention.

EXAMPLES l 9 The experiments listed in the following table were carried out at atmospheric pressure by heating the reactants and the catalyst in a glass flask under reflux.

tively little side reaction, the major portion of the reactants being recovered unchanged. Consequently, the recycle or ultimate yields would approach theoretical.

The results of Example '7 show that a substantial increase in yield was obtained when the reaction was conducted in the presence of anhydrous potassium carbonate.

Examples 5 and 6 show that the reaction is not inhibited by the presence of small amounts of benzene or normal propyl alcohol.

EXAMPLES 10 AND 11 The following examples were carried out under pressure in glass liners in a rotating autoclave. of 850 cc. capacity. Isobutane and carbon tetrachloride were used in Example 10 and normal pentane and chloroform were used in Ex- The yield of tertiary butyl chloride was about of the theoretical based on the carbon tetrachloride oharged. The yield of chloropentane in Example 11 amounted to about 12%.

EXAMPLE 12 An unexpected result was obtained when a solution of 24 g. of hexachloroethane and 3 g. of di-t-butyl peroxide in 10 g. of methyl cyclo- Table I Example No 1 2 3 I 4 6 7 8 9 Hydrogen Donor n-Heptane s u ylcyclohcxane. Halogen Donor Carbon tetrachloride Peroxide Benzoyl peroxide Reactants, g.:

Hydrogen Donor 40 40 40 e 40 l 40 z 40 40 27 30. Halogen Donor" 60 60 B 60 60 60 60 45 20. Peroxide 5 o 5 d 5 5 5 5 h 5 3 3. Temperature, 8 "O s7 s 86 so 85 81 86 92. Duration Hrs 6 7 l 5 17 19 16 17 12 17. Product: b

Formula-" 3 3 01 00111301 01111301. e1d,g 11.7 I 11.6 I 11.8 I 11.9 14. 7 12.1 l 18. 7 2. 4 4.0.

l Flask temperature.

being cooled before each portion was added. d Also 5 g. cadmium turnings.

Also 14 g. anhydrous potassmm carbonate. Includes benzoic acid unless product was washed before distilla- 5 g. benzene.

Also 5 g. n-propyl alcohol. butane.

Benzotriehloride. 1 Toluene.

b Other than chloroform. 6 Added in 1 g. portions at half hour intervals, the flask e Freshly redistilled. Also i 2,3-Dimethyltion. Washed. Some material was lost during reflux due to aleak inastopcock. In each of the experiments listed in the above 5 hexane Was refluxed at at atmospheric table, an amount of chloroform was produced from the carbon tetrachloride that was proportional to the amount of monohalogenated hydrocarbon produced. It can be seen from the results summarized in the table that the yield of chloroheptane in the experiments using heptane was about 20-25% of the theoretical based on the charge. The chloroheptane boiled in the range of ISO-155 C. and had a refractive index,

pressure for three hours. The expected chloromethylcyclohexane was obtained, but tetrachloroethylene and hydrogen chloride were obtained instead of pentachloroethane. Apparently, the pentachloroethane (or its precursor) is relatively unstable and gives up hydrogen chloride readily.

EXAMPLE 13 The following experiment was made to show n h range 1.424-1A30. There was re1a- 7 that carbon tetrachloride and an alkyl chloride EXAMPLE 14 A solution of 23 g. of bicyclo-(2,2,1)-heptane and 42 g. of carbon tetrachloride was refluxed with 8 g. of benzoyl peroxide at 9096 1C. for eighteen hours. The product was washed with dilute alkali, dried and distilled. There was obtained 10 g. of chlorobicyclo-(2,2,1) -heptane, boiling at 59-64 C. at 20 mm. mercury pressure (159-165 C. at 760 mm. pressure) and having a refractive index, 11 of 1.4865-14878.

EXAMPLE 15 A mixture of 40 g. of n-heptane, 60 g. of carbon tetrachloride, 25 g. of water and g. of benzoyl peroxide was refluxed for sixteen hours at 80 C. The product was washed with alkali, dried and distilled. There was obtained 14 g. of chloroheptane boiling chiefly at ISO-151 C. and having a refractive index, n of 1.424.

EXAMPLE 16 A solution of 57 g. of 1,1,1-trichloroethane in 43 g. of n-heptane was refluxed with 5 g. of benzoyl peroxide at 83 C. for sixteen hours. Distillation of the product yielded 5 g. of chloroheptane boiling at ISO-152 0.; n 1427-1428.

We claim as our invention:

1. A hydrogen-halogen exchange process which comprises contacting a halogenated saturated hydrocarbon containing at least two halogen atoms on one of the carbon atoms and a member of the group consisting of saturated hydrocarbons containing more than two carbon atoms and. their monohalogenated derivatives with a compound capable of yielding a free radical at a temperature at least as high as the decomposition temperature of said compound.

2. The process of claim 1 further characterized in that the compound capable of yielding a free radical is a peroxy compound.

3. The process of claim 2 further characterized in that the peroxy compound is an organic peroxide.

4. A hydrogen-chlorine exchange process which comprises contacting a chlorinated saturated hydrocarbon containing at least two chlorine atoms on one of the carbon atoms and a member of the group consisting of saturated hydrocarbons containing mor than two carbon atoms and their monohalogenated derivatives with a compound capable of yielding a'free radical at a temperature at least as high as the decomposition temperature of said compound.

5. The process of claim 4 further characterized in that the compound capable of yielding a free radical is a peroxy compound.

6. The process of claim 5 further characterized in that the peroxy compound is an organic peroxide.

7. A hydrogen-halogen exchange process which comprises contacting a halogenated saturated hydrocarbon containing at least two halogen atoms on one of the carbon atoms and a member of the group consisting of saturated hydrocarbons 6 containing more than two carbon atoms and their monohalogenated derivatives with a-compound capable of yielding a free radical at-a temperature at least as high as the decomposition temperature of said compound and in the presence of aminor amount of an inorganic alkaline substance.

8. The process of claim 7 further characterized in that the compound capable of yielding a free radical is a peroxy compound.

9. The process of claim 8 further characterized in that the peroxy compound is an organic peroxide.

10. A hydrogen-chlorine exchange process which comprises contacting a chlorinated saturated hydrocarbon containing at least two chlorine atoms on one of the carbon atoms and a member of the group consisting of saturated hydrocarbons containing more than two carbon atoms and their monohalogenated derivatives with a compound capable of yielding a free radical at a temperature at least as high as the decomposition temperature of said compound and in the presence of a minor amount of an inorganic alkaline substance.

11. The process of claim 10 further characterized in that the compound capable of yielding a free radical is a peroxy compound.

12. Th process of claim 11 further characterized in that the peroxy compound is an organic peroxide.

13. A hydrogen-chlorine exchange process which comprises contacting carbon tetrachloride and a member of the group consisting of saturated hydrocarbons containing more than two carbon atoms and their monohalogenated derivatives with a compound capable of yielding a free radical at a temperature at least as high as the decomposition temperature of said compound.

14. The process of claim 13 further characterized in that the compound capable of yielding a free radical is a peroxy compound.

15. The process of claim 14 further characterized in that the peroxy compound is an organic peroxide.

16. A process for preparing a chlorobicyclo- (2,2,1) -heptane which comprises contacting carbon tetrachloride and bicyclo-(2,2,1) -heptane with an organic peroxy compound at a temperature at least as high as the decomposition temperature of said compound.

17. A hydrogen-chlorine exchange process which comprises contacting chloroform and a member of the group consisting of saturated hydrocarbons containing more than two carbon atoms and their monohalogenated derivatives with a compound capable of yielding a free radical at a temperature at least as high as the decomposition temperature of said compound.

18. A hydrogen-halogen exchange process which comprises contacting a halogenated saturated hydrocarbon containing at least 2 halogen atoms on one of the carbon atoms and a member of the group consisting of saturated hydrocarbons containing more than 2 carbon atoms and their monohalogenated derivatives with a compound capable of yielding a free radical at a temperature at least as high as the decomposition temperature of said compound and in the presence of water.

19. A hydrogen-chlorine exchange process which comprises contacting a chlorinated saturated hydrocarbon containing at least 2 chlo-' rine atoms on one of the carbon atoms and a member of the group consisting of saturated hydrocarbons containing more than 2 carbon atoms and their monohalogenated derivatives with a compound capable of yielding a free radical at a temperature at least as high as the decomposition temperature of said compound and in th presence of water.

20. The process of claim 19 further characterized in that the compound capable of yielding a free radical is a peroxy compound.

21. The process of claim 20 further characterized in that the peroxy compound is an organic peroxide.

JAMES P. WEST. LOUIS :SCHMERLING.

8 I REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,299,441 Vaughan et al Oct. 20, 1942 2,413,384 Schmerling Dec. 31, 1946 2,501,597 Detling Mar. 21, 1950 OTHER REFERENCES Calingaert et al.: Jour. Am. Chem. 800., vol. 61, pages 2748-54 (1939); vol. 62, pages 1545-7 (1940). 

1. A HYDROGEN-HALOGEN EXCHANGE PROCESS WHICH COMPRISES CONTACTING A HALOGENATED SATURATED HYDROCARBON CONTAINING AT LEAST TWO HALOGEN ATOMS ON ONE OF THE CARBON ATOMS AND A MEMBER OF THE GROUP CONSISTING OF SATURATED HYDROCARBONS CONTAINING MORE THAN TWO CARBON ATOMS AND THEIR MONOHALOGENATED DERIVATIVES WITH A COMPOUND CAPABLE OF YIELDING A FREE RADICAL AT A TEMPERATURE AT LEAST AS HIGH AS THE DECOMPOSITION TEMPERATURE OF SAID COMPOUND. 